A separator for a high energy rechargeable lithium battery and a high energy rechargeable lithium battery are disclosed herein.
A high energy rechargeable lithium battery has an anode with an energy capacity of at least 372 milliampere-hours/gram (mAh/g). Such anodes include, for example, lithium metal, lithium alloys (e.g. lithium aluminum), and mixtures of lithium metal or lithium alloys and materials such as carbon, nickel, and copper. Such anodes exclude anodes solely with lithium intercalation or lithium insertion compounds.
The commercial success of lithium metal or lithium alloy batteries has eluded all but primary cells due to persistent safety problems.
The difficulties associated with the use of the foregoing anodes stem mainly from lithium dendrite growth that occurs after repetitive charge-discharge cycling. (While dendrite growth is a potential problem with any lithium battery, the severity of the problem with the above-mentioned high energy anodes is much greater than with other lithium anodes (e.g. pure carbon intercalation anodes) as is well known in the art.) When lithium dendrites grow and penetrate the separator, an internal short circuit of the battery occurs (any direct contact between anode and cathode is referred to as xe2x80x9celectronicxe2x80x9d shorting, and contact made by dendrites is a type of electronic shorting). Some shorting (i.e., a soft short), caused by very small dendrites, may only reduce the cycling efficiency of the battery. Other shorting may result in thermal runaway of the lithium battery, a serious safety problem for lithium rechargeable battery.
The failure to control the dendrite growth from such anodes remains a problem, limiting the commercialization of cells with those anodes, particularly those cells with liquid organic electrolytes.
Accordingly, there is a need to improve high energy rechargeable lithium batteries.
The instant invention is directed to a separator for a high energy rechargeable lithium battery and the corresponding battery. The separator includes at least one ceramic composite layer and at least one polymeric microporous layer. The ceramic composite layer includes a mixture of inorganic particles and a matrix material. The ceramic composite layer is adapted, at least, to block dendrite growth and to prevent electronic shorting. The polymeric layer is adapted, at least, to block ionic flow between the anode and the cathode in the event of thermal runaway.